Glucose Tolerance Test (GTT)

Some women will also need a Glucose Tolerance Test (GTT) to screen for gestational diabetes (diabetes during pregnancy). Your midwife will ask questions during your booking appointment to assess whether you are at risk of developing gestational diabetes and refer you for the test if necessary. The test is usually done between weeks 24 and 28 of your pregnancy.

If you’ve had gestational diabetes in a previous pregnancy, you’ll be given the test earlier. If it’s negative, the test will be repeated later in the pregnancy. Alternatively, you might be given a blood sugar monitor so that you can check your sugar levels yourself during your pregnancy.

What is a glucose tolerance test? 

A glucose tolerance test is a medical test in which glucose is given to the patient, followed by some blood samples being collected to determine how long it has taken for the glucose to be cleared from the blood. 

The GTT takes about two hours. The first blood sample will be taken in the morning, when you have had nothing to eat or drink overnight or the morning of your test. This includes smoking, chewing gum or medication (unless you’ve been advised to continue to take it – speak to your midwife about this if unsure). You will then be given a special glucose drink, and another blood sample will be taken two hours later.

If you are diagnosed with gestational diabetes, you will be placed under the care of a consultant and a specialist diabetes team to support you and keep you well throughout your GTT pregnancy.